A grand jury shall hear all evidence presented by the district attorney. It may hear evidence for the defendant, but is under no duty to do so.
When the grand jury has reason to believe that other available evidence will explain the charge, it should order the evidence produced.
A grand jury should receive only legal evidence and such as is given by witnesses produced, or furnished by documents and other physical evidence. However, no indictment shall be quashed or conviction reversed on the ground that the indictment was based, in whole or in part, on illegal evidence, or on the ground that the grand jury has violated a provision of this article.